More specifically, the applicant is aware of methods for regulating a voltage Uc between a first and a second output point of a low-pass RLC filter of natural period Tf, this RLC filter including two input points electrically connected, respectively, to the conductors of a DC bus of an electric vehicle powered via a catenary, the first and the second output points being electrically connected to a controllable electric converter for controlling the torque exerted by an electric traction motor of the electric vehicle, the stator time constant τ of this motor being strictly less than the natural period Tf.
These regulation methods include the measurement or estimate of the intensity Ili of a line current Il flowing through the inductance of the filter at an instant ti, of the voltage Uci between the output points of the filter at the instant ti, and of a line voltage Ul between the input points of the filter.
The applicant is also aware of methods for regulating a line current Il flowing through an inductance L of a low-pass RLC filter of natural period Tf, this filter including:                two input points electrically connected, respectively, to the conductors of a DC bus of an electric vehicle powered via a catenary, and        first and second output points, the first and the second output points being electrically connected to a controllable electric converter in order to cause the torque of an electric traction motor of the electric vehicle to vary, the stator time constant τ of this electric motor being strictly less than the natural period Tf.        
These methods include the measurement or estimate of the intensity Ili of the line current Il at an instant ti, of a voltage Uci between the output points of the filter at the instant ti and of a line voltage Ul between the input points of the filter.
Here, the term “catenary” refers to both an overhead line against which a pantograph rubs in order to power the electric vehicle and a ground-based rail against which a contact shoe slides in order to power an electric vehicle. This ground-based rail is more often known by the term “third rail”.
The stator time constant τ of an electric motor is defined by the following relationship:
  τ  =            L              m        ⁢                                              R      m      where:
Lm is the stator inductance of the electric motor, and
Rm is the stator resistance of the electric motor.
This time constant is typically between 4 ms and 200 ms for the electric traction motors of an electric vehicle.
The natural period Tf of the RLC filter is defined by the following formula:Tf=2π√{square root over (LC)}
This natural period Tf must be strictly greater than the time constant τ of the motor, otherwise the RLC filter cannot fulfil its function as a low-pass filter in relation to rapid variations in the current consumed or produced by the motor. Another purpose of the RLC filter is to reduce the source impedance, or the load impedance, as seen by the converter.
The time to speed up the electric motor is defined here as being the time required to cause its speed to vary by a significant fraction, for example 1/1000, of its maximum speed with its maximum torque.
In the known methods, the regulation process involves the use of a feedback loop to establish the difference between a voltage setting Ucc between the output points of the filter or a line current setting Ilc and a measured value. These methods operate correctly but do not provide for reacting quickly enough to sudden variations in the line voltage Ul or resistive torque of the motor. For example, these sudden variations in the line voltage Ul or resistive torque can arise:                if the pantograph becomes detached from the catenary, i.e. when the pantograph loses mechanical and electrical contact with the catenary,        if the pantograph becomes reattached to the catenary, i.e. when the pantograph re-establishes mechanical and electrical contact with the catenary, or        in the event of a loss of adhesion between the drive wheels of the electric vehicle and the wheel bearing structures.        
The invention aims to remedy these problems by proposing a quicker method for regulating the voltage Uc or the line current Il.